Temperature information is used throughout integrated circuits for many purposes. For example, temperature information may be used to monitor whether devices in the integrated circuit are operating outside of optimal operating conditions. Some components, such as certain transistors, may be damaged if operated above a certain temperature due to accelerated dielectric breakdown. Temperature information may be used to decide whether to turn off or slow down operation of the transistor. As another example, temperature information may be used for calibrating outputs from certain components. For example, the output of certain current sources, such as in amplifier systems, may vary based on operating temperature. Temperature information may be used to calibrate the output of those components and normalize operation of the device for various temperatures.
Temperature sensing is conventionally performed through a separate module. The temperature information generated by the sensing operation may then be converted into a desired format. That desired format may be a digital signal when the temperature sensing only provides analog information. Thus, the temperature sensing module may be coupled to an analog-to-digital converter (ADC) module for conversion to the desired digital data format. One example of such an arrangement is shown in FIG. 1. FIG. 1 is a circuit schematic illustrating a conventional temperature sensor based on two bipolar junction (BJT) transistors for coupling to an analog-to-digital converter (ADC). A temperature sensing module 110 may include transistors 114 and 118 coupled to current sources 112 and 116, respectively. The current sources 112 and 116 may be proportional-to-absolute-temperature (PTAT) current sources. The PTAT current sources 112 and 116 generate different current at different temperatures, thus the temperature may be sensed by measuring the currents. The output of PTAT current sources 112 and 116, and thus temperature, may be measured with transistors 114 and 118, respectively, through an analog-to-digital converter (ADC) module 120. The analog-to-digital converter module 120 may be a shared component in an integrated circuit, such that the ADC module 120 may be used to convert temperature information from temperature sensing module 110 when desired or may be used to convert other analog information when desired. Temperature information is obtained by the ADC module 120 for processing by using switches to couple the ADC module 120 to receive voltages across the transistors 114 and 118. In particular, the ADC module 120 may receive VBE1 and VBE2 inputs corresponding to voltages across the base and emitter nodes of the transistors 118 and 114, respectively.
The circuit of FIG. 1 has disadvantages in the use of two transistors 114 and 118 and two current sources 112 and 116. By duplicating elements in an integrated circuit, the size of the integrated circuit is increased and the cost of manufacturing the integrated circuit is increased. Further, to obtain accurate temperature information, the two transistors 114 and 118 must be matched and differentially sampled. This matching requirement increases the cost of the manufacturing process. The differential sampling results in a large number of components, including switches 122, 124, 126, 128, 130, 132, 134, 136, and 138 and capacitors 140 and 142 used to couple the ADC module 120 to the temperature sensing module 110.
Another example configuration for a conventional combination of temperature sensing module and analog-to-digital converter (ADC) module is shown in FIG. 2. FIG. 2 is a circuit schematic illustrating a conventional temperature sensor based on one bipolar junction transistor (BJT) for coupling to an analog-to-digital converter (ADC). The configuration of FIG. 2 includes a single transistor 216 coupled to PTAT current sources 212 and 214 in a temperature sensing module 210. The configuration of FIG. 2 is thus improved over that of FIG. 1 because of the reduction in number of transistors in the temperature sensing module 210. However, an ADC module 220 coupled to the temperature sensing module 210 for processing of the temperature information still includes a number of switches and capacitors 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240. Thus, the reduction of one transistor from the configuration of FIG. 1 results in limited improvements in cost and difficulty of manufacturing the integrated circuit. Further, the configuration of FIG. 2 requires a reference voltage input at node 242. Thus, both of the temperature sensing configurations of FIG. 1 and FIG. 2 and of other prior art temperature sensing configurations results in increased complexity, and thus cost, of manufacturing of integrated circuits containing temperature sensing elements. Further, those configurations result in larger die size due to the additional components for coupling the modules together, resulting in a hindrance to further reducing the size of electronic devices. The additional components also provide more potential for errors and noise sources that reduce accuracy of the temperature sensor in the electronic devices.
Shortcomings mentioned here are only representative and are included simply to highlight that a need exists for improved electrical components, particularly for integrated circuits employed in consumer-level devices, such as mobile phones, mobile computing devices, and media players. Embodiments described herein address certain shortcomings but not necessarily each and every one described here or known in the art.